Implantable hearing devices stimulate internal components of the auditory system and are generally classified into one of two types, namely fully implantable hearing instruments and semi-implantable hearing instruments. In a fully implantable hearing device, the entire instrument is implanted. In a semi-implantable hearing instrument, some of the components, typically the microphone, power supply, and speech signal processor, are externally worn, while the auditory stimulator and key support functions are implanted within the auditory system. The externally worn portion communicates transcutaneously with the implanted portion to provide audio signals that the implanted portion uses to stimulate to the auditory system.
Implanted hearing devices are typically used by individuals with significant loss of hearing function or damage to the auditory system. As a result, they differ in the manner by which the signal is processed and delivered to the patient. The processing step, known in the art as Speech Signal Processing (“SSP”), may include a number of steps such as amplification, frequency shaping, compression, etc. The steps in the SSP are determined by the design of the hearing device, while the particular internal values used in the steps are generated from prescriptive parameters determined by an audiologist. Once a speech processor receives an audio signal (e.g., from a microphone) that is indicative of ambient acoustic signals, a drive signal is produced and provided to an implanted stimulation device that stimulates the hearing impaired person's auditory system. The auditory stimulation may be done acoustically, mechanically, or electrically as a function of the type and severity of the hearing loss in the hearing impaired individual.
By way of example, one type of implantable mechanical stimulator includes an electromechanical transducer having a magnetic coil that drives a vibratory actuator. The actuator is positioned to interface with and stimulate the ossicular chain of the patient via physical engagement. (See e.g., U.S. Pat. No. 5,702,342). In this regard, one or more bones of the ossicular chain are made to mechanically vibrate, which causes the ossicular chain to stimulate the cochlea through its natural input, the so-called oval window. In contrast, a cochlear implant system utilizes an electrode that is inserted into the cochlea to provide electrical stimulation.
In addition to implantable auditory stimulators, other components of implantable hearing instruments may be located subcutaneously (i.e, implanted). By way of example, such additional components may include a receiver for receiving RF signals from an external transmitter and processing electronics to process the received signals and provide an appropriate output signal to an implantable auditory stimulator. In this regard, most implantable hearing devices (i.e., fully and semi-implantable) include an auditory stimulator and an implanted housing that houses such additional components.
In conjunction with implant procedures for attaching an implantable auditory stimulator to the an auditory component of a patient, the various implanted components of a given system may entail positioning at a number of differing locations proximal to the skull (e.g., mastoid process) of a given patient. As will be appreciated, such positioning may require a number of different surgical steps, including for example, the placement of an implantable auditory stimulator through a hole drilled into the mastoid process. Given such positioning requirements, initial component placement can be a challenging procedure and removal/repositioning of selected implanted components of a given implantable hearing aid system (e.g., for reprogramming, replacement, servicing, etc.) may be problematic after the initial implant procedure.